Snap-action electric switch



July 7, 1970 E. B, meow 3,519,112

' SNAP-ACTION ELECTRIC SWITCH Filed Nov. 30, 1967 United States Patent SNAP-ACTION ELECTRIC SWITCH Edward Barnabas Angold, Glenridge Hotel, Callow Hill. Virginia Water, England Filed Nov. 30, 1967, Ser. No. 686,886 Claims priority, application Great Britain, Nov. 30, 1966, 53,728/ 66 Int. Cl. H01h 13/36 US. Cl. 200-67 2 Claims ABSTRACT OF THE DISCLOSURE A snap-action electric switch comprises a rigid moving contact arm which pivots on a pivoted cranked actuating member arranged to be engaged by a switch operating plunger at the end of the cranked member away from its pivot. The contact arm is biased to a particular contact position (e.g., contacts closed position) by a wire spring of generally V-shape which acts to provide an overcentre snap action in operation of the switch and the shaping of the actuating member produces wiping action of the contacts.

This invention relates to electric switches.

According to the present invention there is provided a snap action electric switch comprising cooperating fixed and moving contacts the moving contact of which is carried by a rigid arm which pivots on a switch actuating member which is itself pivoted, said rigid contact carrying arm being urged against the pivot of the actuating member by means of a suitably shaped spring and the switch actuating member being engageable by an operating member (e.g., plunger) at a point on the side of the contact-carrying arm pivot remote from the pivot of the switch actuating member and in a direction substantially tangential to the pivoting of the actuating member about its pivot, such pivotal movement of the actuating member causing initial movement of the contact-carrying arm in its longitudinal direction to effect wiping contact between moving and fixed contacts and subsequent movement of the moving contact in a direction transverse to said longitudinal direction to effect rapid separation of the contacts when the pivot of the contact-carrying arm passes from one side of the line joining the pivot of the actuating member and the point of connection of the spring with the contactcarrying arm to the other side of said line. The spring probably takes the form of a length of springy wire which may be generally V-shaped.

The switch contacts may be arranged for providing a break or changeover action with the moving contact normally being engaged with a fixed contact, in which case the moving contact makes wiping contact with the fixed contact before it disengages therewith in response to pivotal movement of the switch actuating member as the operating plunger is moved generally tangentially to the pivotal movement of the actuating member against the action of the spring. When the arm snaps over centre the moving contact may be arranged for abutting against a back stop arrangement or the other fixed contact of the changeover contacts and upon release of the operating plunger or equivalent the spring is arranged to return the switch to the normal condition.

By way of example a microswitch according to the present invention will now be described with reference to the accompanying diagrammatic drawings, in which FIG. 1 is a diagrammatic side view of the basic switch according to the invention; and

FIG. 2 is a perspective view of a double pole switch utilising a common plunger.

Referring to FIG. 1 of the drawing the switch illustrated comprises a snap action mechanism for the actuation of the switch contacts. The switch shown has a break action with the moving contact I normally engaging with a fixed contact 2. The moving contact 1 is carried by rigid arm 3 which pivots in a recess 4 of a switch actuating member -5 of cranked form which itself pivots at one end thereof in a recess 6 of a fixed fulcrum structure 7. The arm is acted on by a wire spring 8 of generally inverted V-shape which is coupled at one end to the fulcrum structure 7 above the recess 6 and is pivotally connected at its other end to an intermediate point along the arm 3. The wire spring 8 maintains the contact-carrying arm 3 in pivotal connection with member 5. The switch has an operating plunger 9 which is sli'dably mounted so that a part thereof projects through the wall of the switch casing (not shown).

In operation of the switch the operating plunger 9 will be depressed so that a projection 10 thereof imparts clockwise pivotal movement to the member 5. Since the movement of the plunger to produce operation of the switch is relatively small and substantially tangential to the movement at the end of the arm 5 there is negligible sliding or rubbing movement between the plunger 9 and the end of the arm or member 5.

As the arm 5 moves, the fulcrum of the arm 3 moves slightly towards the fixed contact so that the arm 3 moves in its longitudinal direction to afford a wiping movement of the moving contact 1 over the fixed contact 2. The wire spring '8 is only slightly further stressed by such movement; such movement is very small and therefore the force required to displace the operating plunger 9 does not preceptibly increase. When the fulcrum 4 of the arm 3 moves from a position above to one below the line A joining the connections of spring 8 to the arm 3 and the fulcrum structure 7 at point 12 the spring causes the arm 3 to snap over to a position at which the contact 1 disengages with fixed contact 2 and is arrested by a back stop 11. Thus the electrical circuit between the fulcrum member 7 and the fixed contact member 2 will be broken. Upon such operation of the switch the tensioning of the spring 8 is in fact reduced and this actually reduces the pressure required to move the plunger 9 still further. When the plunger 9 is released the wire spring 8 acts to restore the snap mechanism and the switch to its normal condition as depicted in the drawing. The operating forces applied to the plunger 9 and the restoring force exerted on the plunger are dependent upon the spacing d between points 6 and 12. Coincidence between these points (i.e., d=zero) would result in toggle action.

Although the particular embodiment described utilises break contacts it will be obvious that other contact actions, such as make and changeover actions could be employed without departing from the character of the present invention.

As will be appreciated from the foregoing description the switch according to the invention not only provides wiping contact action and snap operation but it achieves these features in an extremely simple and inexpensive manner whilst atfording the advantages of negligible sliding movement between the operating plunger and the switch actuated arm and the avoidance of preceptible increase in pressure required to depress the operating plunger.

FIG. 2 of the drawing shows a double pole snap action microswitch constructed according to the present invention and employing two changeover contact actions. Those parts of the switch which correspond to parts of FIG. 1 have been given the same references. As will be appreciated the switch has two switch mechanisms indicated generally at 13 and 14 each affording snap operation of their appertaining contacts with wiping action as previously described with reference to FIG. 1. In the case of this double 3 pole switch the operating plunger 9 has an inverted T- shaped bottom end piece the two parts of the head of the piece (one only being shown at 15) engaging with the respective members 5 of the two mechanisms 13 and 14. The upper fixed contact carrying members of the two mechanisms which have changeover contact actions are indicated at 16 and 17 and are taken through the base 18 of the insulating casing 19 of the switch to aflford terminals 20. This casing has an integral upstanding wall 21 which isolates the two mechanisms 13 and 14. Further switch terminals 22 and 23 are defined respectively by extensions of the fulcrum members 7 and the contacts 2 projecting through the base 18.

What I claim is:

1. A double pole electric switch comprising two switches as claimed in claim 2, in which the operating member is common to both switches.

2. A snap-action electric switch comprising cooperating fixed and moving contacts; a rigid arm carrying said moving contact; an actuating member, said rigid arm 20 pivotably engaging said switch actuating member; a fulcrum member, said switch actuating member pivotably engaging said fulcrum member; a generally V-shaped spring formed from a length of springy wire, one end of said spring being attached to said rigid arm and the other end thereof being attached to said fulcrum member for urging said rigid arm against the pivot of said actuating member; and an operating member engaging said actu- 4 ating member at a point on the side of said rigid arm pivot remote from the pivot of said actuating member and in a direction substantially tangential to the pivoting of said actuating member about its pivot, said actuating member and rigid arm being disposed to cause, in response to the pivotal movement of said actuating member, initial movement of said rigid arm in its longitudinal direction to effect wiping contact between said moving and fixed contacts and subsequent movement of said moving contact in a direction transverse to said longitudinal direction to effect rapid separation of said contacts when the pivot of said rigid arm passes from one to the other side of the line joining the pivot of said actuating member and the point of connection of said spring with said rigid arm.

References Cited UNITED STATES PATENTS 1,910,510 5/1933 Warner. 2,583,756 1/ 1952 Wahlberg. 3,114,805 12/1963 Baumer. 3,178,528 4/ 1965 Panicci et a1.

FOREIGN PATENTS 1,344,484 10/ 1963 France.

ROBERT K. SCHAEFER, Primary Examiner D. SMITH, JR., Assistant Examiner 

